This invention relates to a signalling method and a conversion device for telecommunications networks. In particular, this invention relates to a signalling method and a conversion device for telecommunications networks in which a multiplicity of subscribers communicate using communications terminals, at least certain of these subscribers being able to register in their home network (H) or in a telecommunications network whose operator has a roaming agreement with the operator of their home network using a first subscriber identification which was assigned to them from the number area of the operator of their home network.
Telecommunications systems are known in which subscribers, using their mobile communications terminals, are able to shift (by means of a so-called roaming) into telecommunications networks which are operated, for example, by foreign network operators. The practical achievement of roaming between telecommunications networks, in particular mobile networks, typically requires reciprocal agreements between the network operators concerned; however, the networks involved first must also have correspondingly suitable mechanisms and devices to enable roaming technically. In particular the Global System for Mobile Communications (GSM) defined by the European Telecommunications Standards Institute (ETSI, F-06921 Sophia Antipolis, Cedex, France) makes it possible for subscribers with mobile communications terminals to shift from the home mobile network (Home Public Land Mobile Network, HPLMN) into visited networks (Visited Public Land Mobile Network, VPLMN). In a GSM mobile network subscriber identifications linked with call numbers and subscriber data are filed in a Home Location Register (HLR) of the HPLMN. The subscriber data comprise, inter alia, information on whereabouts for a respective subscriber, which, for example, is forwarded by a visitor location register (VLR) of a VPLMN to the said HLR. The VLR recognizes the HLR of a visiting subscriber on the basis of his subscriber identification stored in an identification module removably connected to the mobile communications terminal of the subscriber, and forwarded to the VLR by the mobile communications terminal. Either upon request or automatically, the VLR transmits to the HLR a so-called roaming number which is used by the HLR for forwarding calls to the respective mobile communications terminal in the VPLMN. A so-called Mobile Switching Center (MSC) of the GSM network has access to the information filed in the HLR, and serves, inter alia, as the interface between the mobile network and the Public Switched Telephone Network (PSTN), and transmits calls from calling communications terminals to said mobile communications terminals, respectively from said mobile communications terminals to called communications terminals. Although the defined network architecture and the services related thereto support the so-called roaming of mobile communications terminals in VPLMN, this is then only possible, however, generally speaking, if a subscriber is located in the area of a VPLMN with which the operator of his HPLMN has reached a roaming agreement.
Described in the patent GB 2 280 085 A is a method which makes it possible for a subscriber to a first mobile network, e.g. an AMPS/D-AMPS network, to roam in second networks, e.g. GSM networks, a main network of these second mobile networks having a cooperation agreement with the first mobile network and a respective subscriber being handed an identification module which contains an IMSI identifying the subscriber as a visitor to the main network and as a subscriber to the first mobile network. Upon registering in the main network, the respective subscriber is recognized as a visiting subscriber from the first mobile network, and via a communications link and a converter the main network reads subscriber data from the HLR of the first mobile network and stores these in the VLR of the visited main network. Data on the costs for the subscriber in the visited main network are stored in the VLR of the visited main network, and are passed on later to the HLR in the first mobile network, for example by means of a magnetic tape or via a communications link and a converter. Stored in addition in the HLR of the first mobile network is information on the whereabouts of the subscriber in the visited main network of the second mobile network. Under the prerequisite that the first mobile network has a cooperation agreement with the main network of the second mobile network and that the first mobile network is connected to the main network of the second mobile network via a communications link and a converter, a subscriber can, using an identification module which contains an IMSI that identifies the subscriber as a visitor to the main network and as a subscriber of the first mobile network, also roam in a second mobile network with which the operator of the first mobile network has no direct cooperation agreement, with which however the operator of the main network has in each case a cooperation agreement. In the method according to GB 2 280 085 A at least certain subscriber data are stored in the HLR of the main network whereas certain subscriber data are stored only in the HLR of the first mobile network so that during a visit as mentioned to a second mobile network data have to be read from the HLR of the main network and from the HLR of the first mobile network.
It is an object of this invention to propose a new signalling method and a new conversion device for telecommunications networks, which make it possible for subscribers of a home network to visit foreign networks whose operators have no roaming agreement with the operator of their home network, and which do not require any storing of subscriber data in a Home Location Register outside the home network.
In particular this object is attained through the invention in that subscribers to a telecommunications network, in which a multiplicity of subscribers communicate using telecommunications terminals, have not only a first subscriber identification, for example an International Mobile Subscriber Identity (IMSI), which was assigned to each of them from the number area of the operator of their home network and with which they each can register in their home network or in a telecommunications network whose operator has a roaming agreement with the operator of their home network, but each also have a second subscriber identification from the number area of an operator of a partner network, in that such a subscriber, with this second subscriber identification, can register in a foreign network whose operator has no roaming agreement with the operator of his home network, in that the signalling traffic concerning such a subscriber who has registered in a foreign network using his second subscriber identification is passed on to the partner network, in that the signalling traffic in the partner network is filtered, whereby the signalling traffic concerning the subscriber who has registered in said foreign network using his second subscriber identification is rerouted to his home network, and in that the signalling traffic received in the partner network from the home network concerning the subscriber who has registered in a foreign network with his second subscriber identification is rerouted to this foreign network. The telecommunications networks are, for example, mobile radio networks, for example according to GSM, UMTS or another mobile standard, or fixed networks in which subscribers can register themselves by means of identification modules. Such a method has the advantage that a subscriber from a home network, using a subscriber identification from the number area of a partner network, can register in a foreign network with whose operator the operator of his home network has no roaming agreement, the bidirectional signalling traffic between the visited foreign network and the home network being carried out according to conventional standards and being transmitted via the partner network.
During the rerouting of the signalling traffic to the home network, the second subscriber identification contained in a signalling message-protocol data unit, for example a Mobile Application Part (MAP) protocol data unit, is preferably replaced with the first subscriber identification, and during rerouting of the signalling traffic to the foreign network, the first subscriber identification contained in a signalling message-protocol data unit is replaced with the second subscriber identification. This has the advantage that in foreign networks a subscriber is recognized as an authorized subscriber from the partner network on the basis of the second subscriber identification, that in the partner network signalling traffic concerning a subscriber with a second subscriber identification is recognized as signalling traffic to be forwarded to the home network, that in the partner network signalling traffic concerning a subscriber with a first subscriber identification is recognized as signalling traffic to be forwarded to the foreign network, and that in the home network a subscriber is recognized as an authorized subscriber to the home network on the basis of the first subscriber identification.
During rerouting of the signalling traffic to the home network, the addresses, contained in signalling message-protocol data units, of network units of the foreign network, for example the number of a Home Location Register (HLR), a Visitor Location Register (VLR), a Mobile Switching Center (MSC), or a Service Center (SC)xe2x80x94for example a Short Message Service Center (SMSC)xe2x80x94are preferably replaced with addresses of corresponding network units of the partner network, and during the rerouting of the signalling traffic to the foreign network, the addresses, contained in signalling message-protocol data units, of network units of the home network are replaced with addresses of network units of the partner network. This has the advantage that in the home network signalling message protocol data units from the foreign network and in the foreign network signalling message protocol data units from the home network can thus each be considered and treated as signalling message-protocol data units from the partner network.
During rerouting of the signalling traffic to the home network, the address, contained in a signalling connection control message-protocol data unit, for example a Signalling Connection Control Part (SCCP), of a called network unit (Called Party Address) of the partner network is preferably replaced with an address of a network unit of the home network, for example the HLR of the home network, and during the rerouting of the signalling traffic to the foreign network, the address, contained in a signalling connection control message-protocol, of a calling network unit (Calling Party Address) of the home network, for example the HLR of the home network, is replaced with an address of a network unit of the partner network. This has the advantage that a signalling connection control message-protocol data unit from the foreign network, which addresses a called network unit through an address of the partner network, can thereby be re-addressed to a called network unit in the home network, and that a signalling connection control message-protocol data unit from the home network, which contains an address of the home network as the calling network unit, can be passed on to the foreign network with a calling network unit with an address from the partner network.
During the rerouting of the signalling traffic to the home network the address, contained in a signalling connection control message-protocol data unit, for example a Signalling Connection Control Part (SCCP) protocol data unit, of a calling network unit (Calling Party Address) of the foreign network is preferably replaced with an address of a network unit of the partner network, and during the rerouting of the signalling traffic to the foreign network, the address, contained in a signalling connection control message-protocol data unit, of a called network unit (Called Party Address) of the partner network is preferably replaced with an address of a network unit of the foreign network. This has the advantage that a signalling connection control message-protocol data unit from the foreign network, which contains an address of the foreign network as the calling network unit, can be passed on to the home network with a calling network unit with an address from the partner network, and that a signalling connection control message-protocol data unit from the home network, which addresses a called network unit through an address of the partner network, can be re-addressed to a called network unit in the foreign network.
During replacement of the subscriber identifications and/or of addresses of network units, the replacement value is preferably determined in each case according to predefined procedures on the basis of the value to be replaced, for example in that individual digits of a subscriber identification and/or an address of a network unit are deleted, changed or newly added. This has the advantage that it is possible for only certain parts of a subscriber identification and/or address of a network unit to be replaced in a specific way, for example certain parts, which relate to a country and/or a network. The procedures as stored, for example, in one or more procedure tables.
A procedure to be used for the replacement is determined preferably through comparison of the value to be replaced with predefined masks. This has the advantage that it is possible to examine specifically only certain parts of a subscriber identification and/or of an address of a network unit to determine whether the respective subscriber identification and/or address of a network unit is supposed to be replaced, for example certain parts relating to a country and/or a network.
In alternative or complementary embodiment variants, the first and the second subscriber identification are stored for a subscriber in different identification modules or in a common identification module. In the first variant, the respective user of a communications terminal replaces the identification module when he wishes to register in a foreign network, whereas in the second variant the desired subscriber identification is activated manually or automatically.
The objects mentioned above are also achieved in particular by means of the invention in that the conversion device for telecommunications networks, which device can be connected to the signalling system of a first telecommunications network via a first signalling connection and to a second telecommunications network via a second signalling connection, comprises:
a procedure selection table in which masks are stored and numbers of procedure tables linked to these masks;
a comparison module which compares these masks with addresses of network units contained in signalling protocol data units received via said first, respectively second, signalling connections, and, on the basis of the result of this comparison, determines a number of a procedure table;
a conversion module which applies the procedures, contained in the procedure table identified by means of the determined number, for conversion of signalling parameters contained in signalling protocol data units;
a rerouting module that passes on signalling protocol data units with converted signalling parameters via said second, respectively first, signalling connections.
The advantage of such a conversion device consists in that it makes possible the transmission, respectively rerouting, of signalling traffic between telecommunications networks whose operators have no roaming agreement with one another in that addresses (Global Title) and subscriber identifications are analyzed and modified according to predefined procedures without individual subscriber identifications and/or addresses having to be stored. It is moreover very flexible since the described procedures for the conversion device can be adapted to new applications, new network configurations, cooperation agreements or new addresses and can be extended.
The conversion device preferably comprises said procedure tables with predefined procedures according to which the replacement value in each case is determined on the basis of the value to be replaced, when replacing subscriber identifications and/or addresses of network units.
Said procedure tables preferably comprise predefined, stored masks, which are compared with the values to be replaced in order to determine a modification procedure to be used for these values to be replaced.